Code No.B1472: Seat belt pre-tensioner (LH) (squib) system (short-circuited to the earth)
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If diagnosis code B1472 is set in the SRS-ECU, always diagnose the CAN main bus line.
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OPERATION
The SRS-ECU judges how severe a collision is by detecting signals from the front air bag analogue G-sensor. If the impact is over a predetermined level, the SRS-ECU sends an ignition signal. At this time, if the front air bag safing G-sensor is on, the pre-tensioner will deploy.
DIAGNOSIS CODE SET CONDITIONS
This diagnosis code is set if there is abnormal resistance between the input terminals of the seat belt pre-tensioner (LH) (squib).
PROBABLE CAUSES
- Damaged wiring harnesses or connectors
- Short to the earth in the seat belt pre-tensioner (LH) (squib) harness
- Malfunction of the SRS-ECU
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STEP 1. M.U.T.-III CAN bus diagnostics.
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| warning |
Since the radiator fan rotates during CAN bus line diagnostics, make sure that no one is servicing the engine compartment before diagnosing the CAN bus line. Since the CAN communication stops when diagnosing the CAN bus line, the ETACS-ECU detects the time-out of the engine-ECU, and activates the radiator fan to prevent overheating as fail-safe.
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Use the M.U.T.-III to check the CAN bus lines.
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Q.
Is the CAN bus line found to be normal?
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 Go to Step 2.
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 Repair the CAN bus line (Refer to GROUP 54C, Troubleshooting - Can Bus Diagnosis Table  ).
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STEP 2. Check whether the diagnosis code is reset.
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Check again if the diagnosis code is set.
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(1)Erase the diagnosis code.
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(2)Turn the ignition switch to the "ON" position.
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(3)Check if the diagnosis code is set.
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(4)Turn the ignition switch to the "LOCK" (OFF) position.
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Q.
Is the diagnosis code set?
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Go to Step 3.
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There is an intermittent malfunction such as poor engaged connector(s) or open circuit (Refer to GROUP 00, How to Cope with Intermittent Malfunction ).
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STEP 3. Check the seat belt pre-tensioner (LH) (M.U.T.-III diagnosis code).
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(1)Disconnect the negative battery terminal.
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(2)Use a flat-tipped screwdriver to pull out forward and unlock the locking button of the harness side connector, and then disconnect seat belt pre-tensioner (LH) connector C-18.
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(3)Connect special tool dummy resistor (MB991865) to special tool resistor harness (MB991884).
(4)Connect special tool resistor harness (MB991884) to the C-18 harness side connector.
(5)Connect the negative battery terminal.
(6)Erase diagnosis code memory, and check the diagnosis code.
Q.
Is diagnosis code B1472 set?
Go to Step 4.
Replace the seat belt with pre-tensioner (LH) (Refer to ).
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STEP 4. Resistance measurement at the SRS-ECU connector B-109.
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(1)Disconnect the negative battery terminal.
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(2)
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To prevent the seat belt pre-tensioner from deploying unintentionally, disconnect the seat belt pre-tensioner (LH) connector C-18 to short the squib circuit.
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Use a flat-tipped screwdriver to pull out forward and unlock the locking button of the harness side connector, and then disconnect seat belt pre-tensioner (LH) connector C-18.
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(3)Disconnect SRS-ECU connector B-109.
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(4)Resistance measurement between B-109 harness side connector terminals 19, 20 and body earth.
OK: Open circuit
Q.
Are the check results normal?
Go to Step 5.
Repair the harness wires between SRS-ECU connector B-109 (terminal No.19 and 20) and seat belt pre-tensioner (LH) connector C-18 (terminal No.2 and 1).
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STEP 5. Check whether the diagnosis code is reset.
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Q.
Is diagnosis code B1472 set?
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Replace the SRS-ECU (Refer to ).
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An intermittent malfunction is suspected (Refer to GROUP 00, How to Cope with Intermittent Malfunction ).
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